Mouse virus doesn’t cause chronic fatigue syndrome

A RETROVIRUS found in the blood of people with chronic fatigue syndrome probably came from contamination, not infection.

Two years ago, Vincent Lombardi at the Whittemore Peterson Institute in Reno, Nevada, thought he had found the cause of the tiredness and muscle pain of CFS after discovering a mouse virus called xenotropic murine leukaemia virus-related virus (XMRV) in blood samples from 68 of 101 people with CFS compared with just eight of 218 samples from healthy volunteers.

Now, Jay Levy at the University of California, San Francisco, has drawn a blank when screening for XMRV in 61 people with CFS, 43 of whom had tested positive in Lombardi’s study (Science, DOI&colon; 10.1126/science.1204963).

In another study, Vinay Pathak at the National Cancer Institute in Frederick, Maryland, suggests that XMRV originated in lab mice between 1993 and 1996 – after many of the people in Lombardi’s study were diagnosed with CFS – and so cannot be the cause (Science, DOI&colon; 10.1126/science.1205292).

Pathak says that researchers grew cancers in mice without immune systems in order to make prostate tumour tissue for study. The tumour cells picked up two leukaemia viruses which combined to form XMRV. The strains in Lombardi’s samples are so similar to this “recombinant” virus that it is unlikely to have another source, says Pathak.

XMRV has been identified as a contaminant in some lab reagents, which might explain Lombardi’s results.

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